How to debug your charts

A guide for debugging your charts with Google Chrome. All browsers have developer tools and, in-particular, a JavaScript error console that will make debugging your charts much easier.

Debugging your charts becomes an awful lot easier if you use a JavaScript console. This is where you'll find error messages and it's these messages that can help you to trace the location of an error. This page focuses on the developer tools built into Google Chrome, however, each browser has its own set of developer tools. for Mozilla Firefox.

The Google Chrome developer tools in undocked mode

The Google Chrome developer tools in undocked mode

When you first open the developer tools in Google Chrome (you can press CTRL+SHIFT+J to open the tools) they usually look like this - ie in undocked mode. You may prefer this as it gives you more space initially or you may find that showing them in docked mode is more convenient. The button for switching modes is highlighted.


The Google Chrome developer tools in docked mode

Here the tools are docked so that they appear joined to the main browser window at the bottom. Using them this way means that any JavaScript errors will appear in the console which will make debugging your charts much easier.

The Google Chrome developer tools in docked mode

More information

This is an old video from Google IO 2010 detailing the development tools. Remember that other browsers as well as Google Chrome have developer tools - so refer to their documentation for more details.

Debug functions in RGraph

Some functions that you may find very useful when you're debugging your charts are the $c() $a() $p() and $d()functions. The $a() function is just an alias for the standard alert() function and the $p() function is similar but goes further in that it attempts to "pretty print" the structure of whatever you pass it and also gives you type information. The $c() function is an alias for the console.log() function and the $d() function opens a debug window and logs the message to it whilst not blocking execution like the alert() function does. If you need to find out what a variable consists of then this is probably the function you want (or the standard $c() function).